I have Windows 10 on both, and can boot to either, but the 128 is the one I use as default (the 256 is used for software that I use rarely, such as music & Video etc).

I keep them both updated (the 256 probably monthly)

The 128 is now running Winver1709-16299.192, but having updated the 256, I can only get it to get to Winver_1709_16299.125

That I can live with, but the 256 will not show anything if I left click on the start menu button, in spite of me performing 3 restarts, It still refuses to show a start menu.
the 128Gb has no issues like this.

Any idea why this is happening - it can't be hardware, as both use the same hardware, and both are using the same Windows version.

I get a message about shutting down Task Host Window, but there is NO task host window showing in the task bar. Also I get the "Updating" message each time.

As I see it, I could completely rebuild the 256Gb drive (is MCT available for 1709?). If it was reliable, I could use it as the default drive, but with no start menu, it's not feasible.

"Task Host Window is an intelligent windows program which pops up when you attempt to Shut Down windows. The reason why it pops up is due to the running processes and programs in the background; when you initiate shutdown or reboot, task host interrupts the process to check if all running programs were closed to avoid data loss, the pop up would also show you which programs were running. An example of this, would be a notepad file or a word file open, whilst itís open if you attempt to shut down, Task Host window will be shown."